The present invention relates to a folding keyboard for personal computers, word processors and the like.
A variety of folding keyboards have been proposed as in Japanese Pat. Applications Laid-Open Nos. 17723/91 and 148315/90. Any conventional folding keyboard is composed of two rectangular keyboard halves with more frontage than depth and hingedly coupled as a unitary structure which folds in two at the center in its lengthwise direction.
FIG. 1 schematically shows the construction of the folding keyboard disclosed in Japanese Pat. Laid-Open No. 17723/91. This folding keyboard is divided into two at the center thereof and a keyboard enclosure 1 has on either side bearings 2A and 2B connected by a connecting shaft 3 so that the keyboard folds in two. In the folding keyboard structure with the connecting shafts 3 as depicted in FIG. 1, the bearings 2A and 2B project into the plane of key operation from the enclosure 1 and hence encumber the key operation. The disclosure of Japanese Pat. Application Laid-Open No. 17723/91 makes no reference to how an ordinary keyboard assembly having key tops of adjacent arrays displaced from each other is split into two keyboard halves to form the folding structure.
The folding keyboard proposed in Japanese Pat. Application Laid-Open No. 148315/90 has a construction in which two keyboard halves are pivotally secured at opposite ends of their inner marginal edges to both ends of two common flat hinges to form a folding keyboard structure. In this instance, the folding keyboard has two rotary shafts and a suitable selection of the shaft spacing enables the keyboard halves to fold relative to each other with practically no clearance therebetween. Since the flat hinges are protrusively provided on side walls of the keyboard enclosure, however, this conventional folding structure does not look good. Further, since the rotary shafts which connect the two flat hinges to the side walls of the enclosure are each secured thereto at only one side of the hinge, the prior art folding structure is defective in that the rotary shafts readily rattle and are easily deformed by external forces in directions in which the two keyboard halves are twisted relative to each other. The disclosure of Japanese Pat.Application Laid-Open No. 148315/90 is also silent about how the ordinary keyboard having key tops arranged at a different pitch for each array is split into two to form the folding keyboard structure.